study harder or you won't pass the exam 
D. If you study harder , you will pass the exam 

chọn câu d
 

you don't study hard, you won't pass the exam.
18 If I have much money, I can buy a new house.
19 Unless he study harder,he'll fail the exam.
21 If you don't stop telling lies , noone will trust you
22  If you don't pay attention to the teacher, you won't understand the lessons.
23 If you don't go to bed early, you can't get up early the next morning.
24  If you don't save money now, you will be in debt in the future.
25 If you read more books, you can get more knowledge
26 If you don't brush your teeth, you will get toothache.
27 If you don't listen carefully, you won't know what to do.